I do Wordle, Pips, Strands, Connections & Sudoku. Of all of them, I find Connections definitely the hardest, even without the occasional US cultural references that I miss.
I still think the ultimate puzzle is the Sunday crossword (followed closely by Thur-Sat), though Connections is great. And definitely difficult (but never feels unfair).
I cancelled my subscription a few years back due to the way NYT was covering the current administration. At the time, I believed they'd never offer a "puzzles only" subscription because then they'd lose a large part of their subs. But, I was wrong. And now they offer a puzzle-only subscription.
There's a great documentary about the Crossword with Will Shortz that came out about a decade ago that's interesting.
Spelling bee is also pretty consistent.
Just Connections, Wordle, and Mini for me (in that order), with the occasional Crossword (tend towards a barbell strategy of just doing maybe Mon, Tue, Sun to get the quick hits and a real challenging puzzle).
Also experience the odd difficulty due to Americanisms, but can't really fault a puzzle coming from something called the New York Times for that. I do however think the puzzle setting for Connections is inferior to The Wall from Only Connect, where they got the idea from. If you haven't seen that yet it's definitely worth a watch (it gets harder as as a season progresses).